Golf club heads come in many different forms and makes, such as wood- or metal-type (including drivers and fairway woods), iron-type (including wedge-type club heads), utility- or specialty-type, and putter-type. Each of these styles has a prescribed function and make-up. The present invention primarily relates to hollow golf club heads, such as wood-type and utility-type (generally referred to herein as wood-type golf clubs).
Wood-type type golf club heads generally include a front or striking face, a crown, a sole, and an arcuate skirt including a heel, a toe, and a back. The crown and skirt are sometimes referred to as a “shell.” The front face interfaces with and strikes the golf ball. A plurality of grooves, sometimes referred to as “score lines,” may be provided on the face to assist in imparting spin to the ball and for decorative purposes. The crown is generally configured to have a particular look to the golfer and to provide structural rigidity for the striking face. The sole of the golf club contacts and interacts with the ground during the swing.
The design and manufacture of wood-type golf clubs requires careful attention to club head construction. Among the many factors that must be considered are material selection, material treatment, structural integrity, and overall geometrical design. Exemplary geometrical design considerations include loft, lie, face angle, horizontal face bulge, vertical face roll, face size, sole curvature, center of gravity, and overall head weight. In addition, the interior design of the club head may be tailored to achieve particular characteristics, such as by including hosel or shaft attachment means, perimeter weighting on the face or body of the club head, and fillers within hollow club heads.
Club heads typically are formed from stainless steel, aluminum, or titanium, and may be cast, stamped by forming sheet metal with pressure, forged, or formed by a combination of any two or more of these processes. In fact, clubs were originally manufactured primarily by casting durable metallic material such as stainless steel, aluminum, beryllium copper, etc. into a unitary structure comprising a metal body, face, and hosel. However, as technology progressed, it became more desirable to increase the performance of the face of the club, usually by using a titanium material. Today, the club heads may be formed from multiple pieces that are welded or otherwise joined together to form a hollow head, as is often the case of club heads designed with inserts, such as sole plates or crown plates.
The multi-piece constructions facilitate access to the cavity formed within the club head, thereby permitting the attachment of various other components to the head such as internal weights and the club shaft. The cavity may remain empty, or may be partially or completely filled, such as with foam. In addition, due to difficulties in manufacturing one-piece club heads to high dimensional tolerances, the use of multi-piece constructions allows the manufacture of a club head to adhere to a tighter set of standards.
In the case of one-piece heads, it may be necessary to inject an adhesive into the club head to provide the correct swing weight and to collect and retain any debris that may be in the club head. Known in the industry as “rat glue” or “rattle glue” this adhesive is often used in the finishing of hollow club head such as metal drivers and hybrid. The adhesive is typically injected as one of the last steps in the fabrication process, and may be thermoset, or hot-injected and allowed to cool and solidify. In some instances, it is advantageous for the adhesive to remain tacky throughout the life of the club in order to sequester internal debris that is dislocated as the club is used, i.e., due to repeated striking. Typically the adhesive is injected through a small hole in the club head and allowed to distribute throughout the interior.
With a high percentage of amateur golfers constantly searching for more distance on their shots, particularly their drives, the golf industry has responded by providing golf clubs specifically designed with distance in mind. The head sizes of wood-type golf clubs have increased, allowing the club to possess a higher moment of inertia, which translates to a greater ability to resist twisting on off-center hits. As a wood-type club head becomes larger, its center of gravity will be moved back away from the face and further toward the toe, resulting in hits flying higher and further to the right than expected (for right-handed golfers). And, because the center of gravity is moved further away from hosel axis, the larger heads can also cause these clubs to remain open on contact, thereby inducing a “slice” effect (in the case of a right-handed golfer the ball deviates to the right).
While a reduction in loft of a larger club head, offsetting the head, and/or incorporating a hook face angle may help to compensate for this shift in the center of gravity and resulting higher and right-biased hits by “squaring” the face at impact, none of these methods are completely sufficient in solving the issues relating to the larger club heads.
Another technological breakthrough in recent years to provide the average golfer with more distance is to make larger head clubs while keeping the weight constant or even lighter by casting consistently thinner shell thicknesses and using lighter materials such as titanium, magnesium, and composites. Also, the faces of the clubs have been steadily becoming extremely thin, because a thinner face will maximize what is known as the Coefficient of Restitution (COR). For example, the more a face rebounds upon impact, the more energy is imparted to the ball, thereby increasing the resulting shot distance.
With the emphasis on thinner shells, strategic weighting has become important to club manufacturers. Accordingly, weight elements are usually placed at specific locations believed to have a positive influence on the flight of the ball or to overcome a particular golfer's shortcomings. As previously stated, a major problem area of the higher handicap golfer is the tendency to “slice,” which, in addition to deviating the ball to the right, also imparts a greater spin to the ball, thus further reducing the overall shot distance.
As such, a need exists in the art to further enhance weight distribution of a golf club head in order to reduce or eliminate the higher spin and “slice effect” currently an issue with the larger club heads. In addition, it would be advantageous to maximize playability of the club by maximizing the dimensions allowable by the USGA, both heel to toe and face to back. The present invention contemplates such enhancements.